In recent years, air conditioners equipped with an inverter have become wide spread, and reduction in size, performance improvement, reduction in cost and improved reliability are desired.
FIG. 1 is a block diagram showing a conventional compressor driving apparatus. In FIG. 1, inverter circuit 1 and inverter driving circuit 2 are housed in module unit 3. A low voltage direct current supply circuit 5 is adapted to convert a high voltage direct current from high voltage direct current power supply ("HV-DC power supply") 4 into a low voltage direct current for use in the inverter driving circuit 2. A driving signal generating circuit 6 for inverter circuit 1 is connected to the inverter driving circuit 2 through an insulating circuit 7. Circuits 4 through 7 are disposed outside of the module unit 3. Compressor 8 is a load against the inverter circuit 1.
In the prior art, the insulating circuit 7, which comprises photocouplers, etc., is required because an isolation is necessary between the driving signal generating circuit 6 and the module unit 3 from the standpoint of safety. There is a problem, however, that waveforms of an output voltage from the inverter circuit 1 are distorted. This is because a signal developed by the driving signal generating circuit 6 is of relatively high speed, such that a time lag occurs under the influence of the insulating circuit 7.
Moreover, it is required to prepare in advance the data for the driving signal generating circuit 6 for each and every specification of the compressor 8. As a result, it is difficult to standardize a compressor driving section including the driving signal generating circuit 6, the inverter driving circuit 2 and the inverter circuit 1.
In the control system of inverter type air conditioners of the prior art, a compressor driving signal generating section and the compressor driving section for driving the compressor are arranged separately. This results in drawbacks, such as low operating efficiency due to inaccurate operation of a compressor driving power supply (distortion of supply voltage wave forms) and lack of standardization.
An object of the present invention is to resolve the above cited problems of the prior art, and to provide a compressor driving apparatus for air conditioners that results in a smaller size, higher performance and standardization.